How to turn off computer after rendering?
The Alarm and Shutdown add-on can be used.

Alternatively, you can render your scene from the command line, and then add a command to shutdown after it completes (or fails).

On Windows this would be something like:

"C:\path\to\blender.exe" -b "C:\path\to\your file.blend" -a &amp;&amp; shutdown -t 0 -s -f